Form of a rotating shaft and the electrical port is in the form of terminals where AC supply is connected. There are machines available to operate from three phase. remaining chapters cover the modeling and control of AC machines. How- works. First, the construction of a simple two-phase machine is described. THE ROTATING MAGNETIC FIELD; THE INDUCED VOLTAGE IN AC MACHINES; THE INDUCED TORQUE IN AN AC MACHINE; WINDING INSULATION IN AC.


Author: Mrs. Keenan Abshire
Country: Kiribati
Language: English
Genre: Education
Published: 9 March 2017
Pages: 700
PDF File Size: 14.10 Mb
ePub File Size: 50.10 Mb
ISBN: 834-6-22159-191-9
Downloads: 80439
Price: Free
Uploader: Mrs. Keenan Abshire


The flux varies in time, and can also vary in position, or be stationary. To understand how these machines operate, the concept of space vectors or a c machines phasors is introduced.

Electric machine - Wikipedia

Figure 1 — A simple two-pole, single phase synchronous generator, the spatial a c machines of the magnetic field relative to the magnetic axis of the armature winding, and the time dependent induced voltage in the armature winding.

Electric machines often have defined an armature winding which is the winding that is power producing, and a field winding that generates the magnetic field.

Either could be on the stator or rotor depending on the specific a c machines or generator. However it is more common with AC machines such as synchronous or induction machines that the armature winding is on the stator the stationary portion of the motor.


Synchronous machines have field windings on the rotor that is excited by direct current delivered to the rotor windings by slip rings or collector rings by carbon brushes. The field winding produces the north and south poles, thus the image shown in Figure 1 is for a two-pole, single phase one armature winding synchronous generator.

The magnetic axis for a c machines armature winding is perpendicular to the area defined by the armature winding armature winding is the perimeter of this area. This type of machine is often referred to in the literature as a synchronous machine. a c machines

Electric machine

This machine can also be run by connecting the stator coils to a c machines grid, and supplying the rotor coils with AC from an inverter. The advantage is that it is possible to control rotating speed of the machine with a fractionally rated inverter.

When run this way the machine is known as a a c machines double feed "induction" machine. Induction machines[ edit ] Induction machines have short circuited rotor coils where a current is set up and maintained by induction. This requires that the rotor rotates at other than synchronous speed, so that the rotor coils are subjected to a varying magnetic field created by the stator coils.


An induction machine is an asynchronous machine. Induction eliminates the need for brushes which is usually a weak part in an electric machine.

What are AC machines? - Quora

It also allows designs which make it very easy to manufacture the rotor. A metal cylinder will work as rotor, but to improve efficiency a "squirrel cage" rotor or a rotor with closed windings is usually a c machines. The speed of asynchronous induction machines will decrease with increased load because a larger speed difference between stator and rotor is necessary a c machines set up sufficient rotor current and rotor magnetic field.


Asynchronous induction machines can be made so they start and run without any means of control if connected to an AC grid, but the starting torque is low. A special case would be an induction machine a c machines superconductors in the rotor.

The current in the superconductors will be set up by induction, but the rotor will run at synchronous speed because there will be no need for a speed difference between the magnetic field a c machines stator and speed of rotor to maintain the rotor current.

Course On AC Machines, Transformers, Rectifiers and Inverters, Electrical Drives and UPS | EEP

Another special case would be the brushless double fed induction machinewhich has a double set of coils in the stator. Since a c machines has two moving magnetic fields in the stator, it gives no meaning to talk about synchronous or asynchronous speed. Reluctance machines[ edit a c machines Reluctance machines have no windings in rotor, only a ferromagnetic material shaped so that "electromagnets" in stator can "grab" the teeth in rotor and move it a little.

The electromagnets are then turned off, while another set of electromagnets is turned on to move stator further.


Another name a c machines step motor, and it is suited for low speed and accurate position control. Reluctance machines can be supplied with PMs in stator to improve performance.


Electrostatic machines[ edit a c machines In electrostatic machinestorque is created by attraction or repulsion of electric charge in rotor and stator. Electrostatic generators generate electricity by building up electric charge.

Early types were friction machines, later ones were influence machines that worked by electrostatic induction.